Reverse spring lever ink jet printing mechanism

ABSTRACT

An ink jet printer has a reverse spring lever to eject ink from a nozzle chamber. An electromagnetic actuator moves the reverse spring lever from a quiescent position to a pre-firing position and deactivation causes a torsional spring to drive the reverse spring lever to eject ink. The reverse spring lever and the electromagnetic actuator are interconnected in a cantilever arrangement such that small movements of the electromagnetic actuator result in larger movements of the reverse spring lever. The first actuator includes a solenoid coil surrounded by a magnetic actuator having a first fixed magnetic pole and a second moveable magnetic pole. The moveable magnetic pole includes a number of slots for the flow of ink through that pole upon movement.

CROSS REFERENCES TO RELATED APPLICATIONS

The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, U.S. patent applications identified by their U.S. patent application Ser. No. (USSN) are listed alongside the Australian applications from which the U.S. patent applications claim the right of priority.

U.S. Pat. No./ CROSS- PATENT APPLICATION REFERENCED (CLAIMING RIGHT AUSTRALIAN OF PRIORITY PROVISIONAL FROM AUSTRALIAN PATENT PROVISIONAL APPLICATION NO. APPLICATION) DOCKET NO. PO7991 09/113,060 ART01 PO8505 09/113,070 ART02 PO7988 09/113,073 ART03 PO9395 09/112,748 ART04 PO8017 09/112,747 ART06 PO8014 09/112,776 ART07 PO8025 09/112,750 ART08 PO8032 09/112,746 ART09 PO7999 09/112,743 ART10 PO7998 09/112,742 ART11 PO8031 09/112,741 ART12 PO8030 09/112,740 ART13 PO7997 09/112,739 ART15 PO7979 09/113,053 ART16 PO8015 09/112,738 ART17 PO7978 09/113,067 ART18 PO7982 09/113,063 ART19 PO7989 09/113,069 ART20 PO8019 09/112,744 ART21 PO7980 09/113,058 ART22 PO8018 09/112,777 ART24 PO7938 09/113,224 ART25 PO8016 09/112,804 ART26 PO8024 09/112,805 ART27 PO7940 09/113,072 ART28 PO7939 09/112,785 ART29 PO8501 09/112,797 ART30 PO8500 09/112,796 ART31 PO7987 09/113,071 ART32 PO8022 09/112,824 ART33 PO8497 09/113,090 ART34 PO8020 09/112,823 ART38 PO8023 09/113,222 ART39 PO8504 09/112,786 ART42 PO8000 09/113,051 ART43 PO7977 09/112,782 ART44 PO7934 09/113,056 ART45 PO7990 09/113,059 ART46 PO8499 09/113,091 ART47 PO8502 09/112,753 ART48 PO7981 09/113,055 ART50 PO7986 09/113,057 ART51 PO7983 09/113,054 ART52 PO8026 09/112,752 ART53 PO8027 09/112,759 ART54 PO8028 09/112,757 ART56 PO9394 09/112,758 ART57 PO9396 09/113,107 ART58 PO9397 09/112,829 ART59 PO9398 09/112,792 ART60 PO9399  6,106,147 ART61 PO9400 09/112,790 ART62 PO9401 09/112,789 ART63 PO9402 09/112,788 ART64 PO9403 09/112,795 ART65 PO9405 09/112,749 ART66 PP0959 09/112,784 ART68 PP1397 09/112,783 ART69 PP2370 09/112,781 DOT01 PP2371 09/113,052 DOT02 PP8003 09/112,834 Fluid01 PO8005 09/113,103 Fluid02 PO9404 09/113,101 Fluid03 PO8066 09/112,751 IJ01 PO8072 09/112,787 IJ02 PO8040 09/112,802 IJ03 PO8071 09/112,803 IJ04 PO8047 09/113,097 IJ05 PO8035 09/113,099 IJ06 PO8044 09/113,084 IJ07 PO8063 09/113,066 IJ08 PO8057 09/112,778 IJ09 PO8056 09/112,779 IJ10 PO8069 09/113,077 IJ11 PO8049 09/113,061 IJ12 PO8036 09/112,818 IJ13 PO8048 09/112,816 IJ14 PO8070 09/112,772 IJ15 PO8067 09/112,819 IJ16 PO8001 09/112,815 IJ17 PO8038 09/113,096 IJ18 PO8033 09/113,068 IJ19 PO8002 09/113,095 IJ20 PO8068 09/112,808 IJ21 PO8062 09/112,809 IJ22 PO8034 09/112,780 IJ23 PO8039 09/113,083 IJ24 PO8041 09/113,121 IJ25 PO8004 09/113,122 IJ26 PO8037 09/112,793 IJ27 PO8043 09/112,794 IJ28 PO8042 09/113,128 IJ29 PO8064 09/113,127 IJ30 PO9389 09/112,756 IJ31 PO9391 09/112,755 IJ32 PP0888 09/112,754 IJ33 PP0891 09/112,811 IJ34 PP0890 09/112,812 IJ35 PP0873 09/112,813 IJ36 PP0993 09/112,814 IJ37 PP0890 09/112,764 IJ38 PP1398 09/112,765 IJ39 PP2592 09/112,767 IJ40 PP2593 09/112,768 IJ41 PP3991 09/112,807 IJ42 PP3987 09/112,806 IJ43 PP3985 09/112,820 IJ44 PP3983 09/112,821 IJ45 PO7935 09/112,822 IJM01 PO7936 09/112,825 IJM02 PO7937 09/112,826 IJM03 PO8061 09/112,827 IJM04 PO8054 09/112,828 IJM05 PO8065  6,071,750 IJM06 PO8055 09/113,108 IJM07 PO8053 09/113,109 IJM08 PO8078 09/113,123 IJM9 PO7933 09/113,114 IJM10 PO7950 09/113,115 IJM11 PO7949 09/113,129 IJM12 PO8060 09/113,124 IJM13 PO8059 09/113,125 IJM14 PO8073 09/113,126 IJM15 PO8076 09/113,119 IJM16 PO8075 09/113,120 IJM17 PO8079 09/113,221 IJM18 PO5050 09/113,116 IJM19 PO8052 09/113,118 IJM20 PO7948 09/113,117 IJM21 PO7951 09/113,113 IJM22 PO8074 09/113,130 IJM23 PO7941 09/113,110 IJM24 PO8077 09/113,112 IJM25 PO8058 09/113,087 IJM26 PO8051 09/113,074 IJM27 PO8045  6,111,754 IJM28 PO7952 09/113,088 IJM29 PO8046 09/112,771 IJM30 PO9390 09/112,769 IJM31 PO9392 09/112,770 IJM32 PP0889 09/112,798 IJM35 PP0887 09/112,801 IJM36 PP0882 09/112,800 IJM37 PP0874 09/112,799 IJM38 PP1396 09/113,098 IJM39 PP3989 09/112,833 IJM40 PP2591 09/112,832 IJM41 PP3990 09/112,831 IJM42 PP3986 09/112,830 IJM43 PP3984 09/112,836 IJM44 PP3982 09/112,835 IJM45 PP0895 09/113,102 IR01 PP0870 09/113,106 IR02 PP0869 09/113,105 IR04 PP0887 09/113,104 IR05 PP0885 09/112,810 IR06 PP0884 09/112,766 IR10 PP0886 09/113,085 IR12 PP0871 09/113,086 IR13 PP0876 09/113,094 IR14 PP0877 09/112,760 IR16 PP0878 09/112,773 IR17 PP0879 09/112,774 IR18 PP0883 09/112,775 IR19 PP0880  6,152,619 IR20 PP0881 09/113,092 IR21 PO8006  6,087,638 MEMS02 PO8007 09/113,093 MEMS03 PO8008 09/113,062 MEMS04 PO8010  6,041,600 MEMS05 PO8011 09/113,082 MEMS06 PO7947  6,067,797 MEMS07 PO7944 09/113,080 MEMS09 PO7946  6,044,646 MEMS10 PO9393 09/113,065 MEMS11 PP0875 09/113,078 MEMS12 PP0894 09/113,075 MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to ink jet printing and in particular discloses a reverse spring level ink jet printer.

The present invention further relates to the field of drop on demand ink jet printing.

BACKGROUND OF THE INVENTION

Many different types of printing have been invented, a large number of which are presently in use. The known forms of print have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.

In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature.

Many different techniques on ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, “Non-Impact Printing: Introduction and Historical Perspective”, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207 to 220 (1988).

Ink Jet printers themselves come in many different types. The utilisation of a continuous stream ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electrostatic ink jet printing.

U.S. Pat. No. 3,596,275 by Sweet also discloses a process of a continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al)

Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. 4,584,590 which discloses a shear mode type of piezoelectric transducer element.

Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclosed ink jet printing techniques rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.

As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an alternative form of drop on demand ink jet printing utilizing a reverse spring lever arrangement to actuate the ejection of ink from a nozzle chamber.

In accordance with a first aspect of the present invention an ink jet printing nozzle apparatus with a connected ink supply chamber, the apparatus comprising an ink ejection means having one surface in fluid communication with the ink in the nozzle chamber, a recoil means connected to the ink ejection means and a first actuator means connected to the ink ejection means. The method of ejecting ink from the ink chamber comprises the steps of activation of the first actuator means which drives the ink ejection means from a quiescent position to a pre-firing position and deactivation of the first actuator means, causing the recoil means to drive the ink ejection means to eject ink from the nozzle chamber through the ink ejection port. Further, the recoil means includes a resilient member and the movement of the first actuator results in resilient movement of this recoil means and the driving of the ink ejection means comprises the resilient member acting upon the ink ejection means. Preferably, the first actuator means comprises an electromagnetic actuator and the recoil means comprises a torsional spring. The ink ejection means and the first actuator are interconnected in a cantilever arrangement wherein small movements of the first actuator means result in larger movements of the ink ejection means. Advantageously, the recoil means is located substantially at the pivot point of the cantilever construction. The first actuator includes a solenoid coil surrounded by a magnetic actuator having a first mixed magnetic pole and a second moveable magnetic pole, such that, upon activation of the coil, the poles undergo movement relative to one another with the moveable magnetic pole being connected to the actuator side of the cantilever construction. Preferably, the moveable magnetic pole includes a plurality of slots for the flow of ink through the pole upon movement. The ink ejection means comprises a piston or plunger or having a surface substantially mating with at least one surface of the nozzle chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings which:

FIG. 1 is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with the preferred embodiment;

FIG. 2 is a perspective view, in part in section, of a single ink jet nozzle constructed in accordance with the preferred embodiment;

FIG. 3 provides a legend of the materials indicated in FIG. 4 to 20; and

FIG. 4 to FIG. 20 illustrate sectional views of the manufacturing steps in one form of construction of an ink jet print head nozzle.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

The preferred embodiment of the present invention relies upon a magnetic actuator to “load” a spring, such that, upon deactivation of the magnetic actuator the resultant movement of the spring causes ejection of a drop of ink as the spring returns to its original position.

Turning to FIG. 1, there is illustrated an exploded perspective view of an ink nozzle arrangement 1 constructed in accordance with the preferred embodiment. It would be understood that the preferred embodiment can be constructed as an array of nozzle arrangements 1 so as to together form a line for printing.

The operation of the ink nozzle arrangement 1 of FIG. 1 proceeds by a solenoid 2 being energized by way of a driving circuit 3 when it is desired to print out a ink drop. The energized solenoid 2 induces a magnetic field in a fixed soft magnetic pole 4 and a moveable soft magnetic pole 5. The solenoid power is turned on to a maximum current for long enough to move the moveable pole 5 from its rest position to a stopped position close to the fixed magnetic pole 4. The ink nozzle arrangement 1 of FIG. 1 sits within an ink chamber filled with ink. Therefore, holes 6 are provided in the moveable soft magnetic pole 5 for “squirting” out of ink from around the coil 2 when the pole 5 undergoes movement.

The moveable soft magnetic pole is balanced by a fulcrum 8 with a piston head 9. Movement of the magnetic pole 5 closer to the stationary pole 4 causes the piston head 9 to move away from a nozzle chamber 11 drawing air into the chamber 11 via an ink ejection port 13. The piston 9 is then held open above the nozzle chamber 11 by means of maintaining a low “keeper” current through solenoid 2. The keeper level current through solenoid 2 being sufficient to maintain the moveable pole 5 against the fixed soft magnetic pole 4. The level of current will be substantially less than the maximum current level because the gap between the two poles 4 and 5 is at a minimum. For example, a keeper level current of 10% of the maximum current level may be suitable. During this phase of operation, the meniscus of ink at the nozzle tip or ink ejection port 13 is a concave hemisphere due to the in flow of air. The surface tension on the meniscus exerts a net force on the ink which results in ink flow from the ink chamber into the nozzle chamber 11. This results in the nozzle chamber refilling, replacing the volume taken up by the piston head 9 which has been withdrawn. This process takes approximately 100 μs.

The current within solenoid 2 is then reversed to half that of the maximum current. The reversal demagnetises the magnetic poles and initiates a return of the piston 9 to its rest position. The piston 9 is moved to its normal rest position by both the magnetic repulsion and by the energy stored in a stressed tortional spring 16, 19 which was put in a state of torsion upon the movement of moveable pole 5.

The forces applied to the piston 9 as a result of the reverse current and spring 16, 19 will be greatest at the beginning of the movement of the piston 9 and will decrease as the spring elastic stress falls to zero. As a result, the acceleration of piston 9 is high at the beginning of a reverse stroke and the resultant ink velocity within the chamber 11 becomes uniform during the stroke. This results in an increased operating tolerance before ink flow over the print head surface will occur.

At a predetermined time during the return stroke, the solenoid reverse current is turned off. The current is turned off when the residual magnetism of the movable pole is at a minimum. The piston 9 continues to move towards its original rest position.

The piston 9 will overshoot the quiescent or rest position due to its inertia. Overshoot in the piston movement achieves two things: greater ejected drop volume and velocity, and improved drop break off as the piston returns from overshoot to its quiescent position.

The piston 9 will eventually return from overshoot to the quiescent position. This return is caused by the springs 16, 19 which are now stressed in the opposite direction. The piston return “sucks” some of the ink back into the nozzle chamber 11, causing the ink ligament connecting the ink drop to the ink in the nozzle chamber 11 to thin. The forward velocity of the drop and the backward velocity of the ink in the nozzle chamber 11 are resolved by the ink drop breaking off from the ink in the nozzle chamber 11.

The piston 9 stays in the quiescent position until the next drop ejection cycle.

A liquid ink print head has one ink nozzle arrangement 1 associated with each of the multitude of nozzles. The arrangement 1 has the following major parts:

(1) Drive circuitry 3 for driving the solenoid 2.

(2) An ejection port 13. The radius of the ejection port 13 is an important determinant of drop velocity and drop size.

(3) A piston 4. This is a cylinder which moves through the nozzle chamber 11 to expel the ink. The piston 9 is connected to one end of the lever arm 17. The piston radius is approximately 1.5 to 2 times the radius of the ejection port 13. The ink drop volume output is mostly determined by the volume of ink displaced by the piston 9 during the piston return stroke.

(4) A nozzle chamber 11. The nozzle chamber 11 is slightly wider than the piston 9. The gap between the piston 9 and the nozzle chamber walls is as small as is required to ensure that the piston does not contact the nozzle chamber during actuation or return. If the printheads are fabricated using 0.5 μm semiconductor lithography, then a 1 μm gap will usually be sufficient. The nozzle chamber is also deep enough so that air ingested through the ejection port 13 when the plunger 9 returns to its quiescent state does not extend to the piston 9. If it does, the ingested bubble may form a cylindrical surface instead of a hemispherical surface. If this happens, the nozzle will not refill properly.

(5) A solenoid 2. This is a spiral coil of copper. Copper is used for its low resistivity, and high electro-migration resistance.

(6) A fixed magnetic pole of ferromagnetic material 4.

(7) A moveable magnetic pole of ferromagnetic material 5. To maximise the magnetic force generated, the moveable magnetic pole 5 and fixed magnetic pole 4 surround the solenoid 2 as a torus. Thus little magnetic flux is lost, and the flux is concentrated across the gap between the moveable magnetic pole 5 and the fixed pole 4. The moveable magnetic pole 5 has holes in the surface 6 (FIG. 1) above the solenoid to allow trapped ink to escape. These holes are arranged and shaped so as to minimise their effect on the magnetic force generated between the moveable magnetic pole 5 and the fixed magnetic pole 4.

(8) A magnetic gap. The gap between the fixed plate 4 and the moveable magnetic pole 5 is one of the most important “parts” of the print actuator. The size of the gap strongly affects the magnetic force generated, and also limits the travel of the moveable magnetic pole 5. A small gap is desirable to achieve a strong magnetic force. The travel of the piston 9 is related to the travel of the moveable magnetic pole 5 (and therefore the gap) by the lever arm 17.

(9) Length of the lever arm 17. The lever arm 17 allows the travel of the piston 9 and the moveable magnetic pole 5 to be independently optimised. At the short end of the lever arm 17 is the moveable magnetic pole 5. At the long end of the lever arm 17 is the piston 9. The spring 16 is at the fulcrum 8. The optimum travel for the moveable magnetic pole 5 is less than 1 mm, so as to minimise the magnetic gap. The optimum travel for the piston 9 is approximately 5 μm for a 1200 dpi printer. The difference in optimum travel is resolved by a lever 17 with a 5:1 or greater ratio in arm length.

(10) Springs 16, 19 (FIG. 1). The springs eg. 16 return the piston to its quiescent position after a deactivation of the actuator. The springs 16 are at the fulcrum 8 of the lever arm.

(11) Passivation layers (not shown). Al surfaces are preferably coated with passivation layers, which may be silicon nitride (Si₃N₄), diamond like carbon (DLC), or other chemically inert, highly impermeable layer. The passivation layers are especially important for device lifetime, as the active device is immersed in the ink. As will be evident from the foregoing description there is an advantage in ejecting the drop on deactivation of the solenoid 2. This advantage comes from the rate of acceleration of the moving magnetic pole 5 which is used as a piston or plunger.

The force produced by a moveable magnetic pole by an electromagnetic induced field is approximately proportional to the inverse square of the gap between the moveable 5 and static magnetic poles 4. When the solenoid 2 is off, this gap is at a maximum. When the solenoid 2 is turned on, the moving pole 5 is attracted to the static pole 4. As the gap decreases, the force increases, accelerating the movable pole 5 faster. The velocity increases in a highly non-linear fashion, approximately with the square of time. During the reverse movement of the moving pole 5 upon deactivation the acceleration of the moving pole 5 is greatest at the beginning and then slows as the spring elastic stress falls to zero. As a result, the velocity of the moving pole 5 is more uniform during the reverse stroke movement.

(1) The velocity of piston or plunger 9 is much more constant over the duration of the drop ejection stroke.

(2) The piston or plunger 9 can readily be entirely removed from the ink chamber during the ink fill stage, and thereby the nozzle filling time can be reduced, allowing faster printhead operation.

However, this approach does have some disadvantages over a direct firing type of actuator:

(1) The stresses on the spring 16 are relatively large. Careful design is required to ensure that the springs operate at below the yield strength of the materials used.

(2) The solenoid 2 must be provided with a “keeper” current for the nozzle fill duration. The keeper current will typically be less than 10% of the solenoid actuation current. However, the nozzle fill duration is typically around 50 times the drop firing duration, so the keeper energy will typically exceed the solenoid actuation energy.

(3) The operation of the actuator is more complex due to the requirement for a “keeper” phase.

The printhead is fabricated from two silicon wafers. A first wafer is used to fabricate the print nozzles (the printhead wafer) and a second wafer (the Ink Channel Wafer) is utilised to fabricate the various ink channels in addition to providing a support means for the first channel. The fabrication process then proceeds as follows:

(1) Start with a single crystal silicon wafer 20, which has a buried epitaxial layer 22 of silicon which is heavily doped with boron. The boron should be doped to preferably 10²⁰ atoms per cm³ of boron or more, and be approximately 3 μm thick, and be doped in a manner suitable for the active semiconductor device technology chosen. The wafer diameter of the printhead wafer should be the same as the ink channel wafer.

(2) Fabricate the drive transistors and data distribution circuitry 3 according to the process chosen (eg. CMOS).

(3) Planarise the wafer 20 using chemical Mechanical Planarisation (CMP).

(4) Deposit 5 mm of glass (SiO₂) over the second level metal.

(5) Using a dual damascene process, etch two levels into the top oxide layer. Level 1 is 4 μm deep, and level 2 is 5 μm deep. Level 2 contacts the second level metal. The masks for the static magnetic pole are used.

(6) Deposit 5 μm of nickel iron alloy (NiFe).

(7) Planarise the wafer using CMP, until the level of the SiO₂ is reached forming the magnetic pole 4.

(8) Deposit 0.1 μm of silicon nitride (Si₃N₄).

(9) Etch the Si₃N₄ for via holes for the connections to the solenoids, and for the nozzle chamber region 11.

(10) Deposit 4 μm of SiO₂.

(11) Plasma etch the SiO₂ in using the solenoid and support post mask.

(12) Deposit a thin diffusion barrier, such as Ti, TiN, or TiW, and an adhesion layer if the diffusion layer chosen has insufficient adhesion.

(13) Deposit 4 μm of copper for forming the solenoid 2 and spring posts 24. The deposition may be by sputtering, CVD, or electroless plating. As well as lower resistivity than aluminum, copper has significantly higher resistance to electro-migration. The electro-migration resistance is significant, as current densities in the order of 3×10⁶ Amps/cm² may be required. Copper films deposited by low energy kinetic ion bias sputtering have been found to have 1,000 to 100,000 times larger electro-migration lifetimes larger than aluminum silicon alloy. The deposited copper should be alloyed and layered for maximum electro-migration lifetimes than aluminum silicon alloy. The deposited copper should be alloyed and layered for maximum electro-migration resistance, while maintaining high electrical conductivity.

(14) Planarise the wafer using CMP, until the level of the SiO₂ is reached. A damascene process is used for the copper layer due to the difficulty involved in etching copper. However, since the damascene dielectric layer is subsequently removed, processing is actually simpler if a standard deposit/etch cycle is used instead of damascene. However, it should be noted that the aspect ratio of the copper etch would be 8:1 for this design, compared to only 4:1 for a damascene oxide etch. This difference occurs because the copper is 1 μm wide and 4 μm thick, but has only 0.5 μm spacing. Damascene processing also reduces the lithographic difficultly, as the resist is on oxide, not metal.

(15) Plasma etch the nozzle chamber 11, stopping at the boron doped epitaxial silicon layer 21. This etch will be through around 13 μm of SiO₂, and 8 μm of silicon. The etch should be highly anisotropic, with near vertical sidewalls. The etch stop detection can be on boron in the exhaust gasses. If this etch is selective against NiFe, the masks for this step and the following step can be combined, and the following step can be eliminated. This step also etches the edge of the printhead wafer down to the boron layer, for later separation.

(16) Etch the SiO₂ layer. This need only be removed in the regions above the NiFe fixed magnetic poles, so it can be removed in the previous step if an Si and SiO₂ etch selective against NiFe is used.

(17) Conformably deposit 0.5 μm of high density Si₃N₄. This forms a corrosion barrier, so should be free of pin-holes, and be impermeable to OH ions.

(18) Deposit a thick sacrificial layer 40. This layer should entirely fill the nozzle chambers, and coat the entire wafer to an added thickness of 8 μm. The sacrificial layer may be SiO₂.

(19) Etch two depths in the sacrificial layer for a dual damascene process. The deep etch is 8 μm, and the shallow etch is 3 μm. The masks defines the piston 9, the lever arm 17, the springs 16 and the moveable magnetic pole 5.

(20) Conformably deposit 0.1 μm of high density Si₃N₄. This forms a corrosion barrier, so should be free of pin-holes, and be impermeable to OH ions.

(21) Deposit 8 μm of nickel iron alloy (NiFe).

(22) Planarise the wafer using CMP, until the level of the SiO₂ is reached.

(23) Deposit 0.1 μm of silicon nitride (Si₃N₄).

(24) Etch the Si₃N₄ everywhere except the top of the plungers.

(25) Open the bond pads.

(26) Permanently bond the wafer onto a pre-fabricated ink channel wafer. The active side of the printhead wafer faces the ink channel wafer. The ink channel wafer is attached to a backing plate, as it has already been etched into separate ink channel chips.

(27) Etch the printhead wafer to entirely remove the backside silicon to the level of the boron doped epitaxial layer 22. This etch can be a batch wet etch in ethylenediamine pyrocatechol (EDP).

(28) Mask the nozzle rim 14 from the underside of the printhead wafer. This mask also includes the chip edges.

(31) Etch through the boron doped silicon layer 22, thereby creating the nozzle holes. This etch should also etch fairly deeply into the sacrificial material in the nozzle chambers to reduce time required to remove the sacrificial layer.

(32) Completely etch the sacrificial material. If this material is SiO₂ then a HF etch can be used. The nitride coating on the various layers protects the other glass dielectric layers and other materials in the device from HF etching. Access of the HF to the sacrificial layer material is through the nozzle, and simultaneously through the ink channel chip. The effective depth of the etch is 21 μm.

(33) Separate the chips from the backing plate. Each chip is now a full printhead including ink channels. The two wafers have already been etched through, so the printheads do not need to be diced.

(34) Test the printheads and TAB bond the good printheads.

(35) Hydrophobise the front surface of the printheads.

(36) Perform final testing on the TAB bonded printheads.

FIG. 2 shows a perspective view, in part in section, of a single ink jet nozzle arrangement 1 constructed in accordance with the preferred embodiment.

One alternative form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:

1. Using a double sided polished wafer deposit 3 microns of epitaxial silicon heavily doped with boron.

2. Deposit 10 microns of epitaxial silicon, either p-type or n-type, depending upon the CMOS process used.

3. Complete a 0.5 micron, one poly, 2 metal CMOS process. This step is shown in FIG. 4. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. FIG. 3 is a key to representations of various materials in these manufacturing diagrams.

4. Etch the CMOS oxide layers down to silicon or aluminum using Mask 1. This mask defines the nozzle chamber, the edges of the printheads chips, and the vias for the contacts from the aluminum electrodes to the two halves of the split fixed magnetic plate.

5. Plasma etch the silicon down to the boron doped buried layer, using oxide from step 4 as a mask. This etch does not substantially etch the aluminum. This step is shown in FIG. 5.

6. Deposit a seed layer of cobalt nickel iron alloy. CoNiFe is chosen due to a high saturation flux density of 2 Tesla, and a low coercivity. [Osaka, Tetsuya et al, A soft magnetic CoNiFe film with high saturation magnetic flux density, Nature 392, 796-798 (1998)].

7. Spin on 4 microns of resist, expose with Mask 2, and develop. This mask defines the split fixed magnetic plate and the nozzle chamber wall, for which the resist acts as an electroplating mold. This step is shown in FIG. 6.

8. Electroplate 3 microns of CoNiFe. This step is shown in FIG. 7.

9. Strip the resist and etch the exposed seed layer. This step is shown in FIG. 8.

10. Deposit 0.1 microns of silicon nitride (Si3N4).

11. Etch the nitride layer using Mask 3. This mask defines the contact vias from each end of the solenoid coil to the two halves of the split fixed magnetic plate.

12. Deposit a seed layer of copper. Copper is used for its low resistivity (which results in higher efficiency) and its high electromigration resistance, which increases reliability at high current densities.

13. Spin on 5 microns of resist, expose with Mask 4, and develop. This mask defines the solenoid spiral coil, the nozzle chamber wall and the spring posts, for which the resist acts as an electroplating mold. This step is shown in FIG. 9.

14. Electroplate 4 microns of copper.

15. Strip the resist and etch the exposed copper seed layer. This step is shown in FIG. 10.

16. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated.

17. Deposit 0.1 microns of silicon nitride.

18. Deposit 1 micron of sacrificial material. This layer determines the magnetic gap.

19. Etch the sacrificial material using Mask 5. This mask defines the spring posts and the nozzle chamber wall. This step is shown in FIG. 11.

20. Deposit a seed layer of CoNiFe.

21. Spin on 4.5 microns of resist, expose with Mask 6, and develop. This mask defines the walls of the magnetic plunger, the lever arm, the nozzle chamber wall and the spring posts. The resist forms an electroplating mold for these parts. This step is shown in FIG. 12.

22. Electroplate 4 microns of CoNiFe. This step is shown in FIG. 13.

23. Deposit a seed layer of CoNiFe.

24. Spin on 4 microns of resist, expose with Mask 7, and develop. This mask defines the roof of the magnetic plunger, the nozzle chamber wall, the lever arm, the springs, and the spring posts. The resist forms an electroplating mold for these parts. This step is shown in FIG. 14.

25. Electroplate 3 microns of CoNiFe. This step is shown in FIG. 15.

26. Mount the wafer on a glass blank and back-etch the wafer using KOH, with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer. This step is shown in FIG. 16.

27. Plasma back-etch the boron doped silicon layer to a depth of 1 micron using Mask 8. This mask defines the nozzle rim. This step is shown in FIG. 17.

28. Plasma back-etch through the boron doped layer using Mask 9. This mask defines the nozzle, and the edge of the chips. At this stage, the chips are separate, but are still mounted on the glass blank. This step is shown in FIG. 18.

29. Detach the chips from the glass blank. Strip all adhesive, resist, sacrificial, and exposed seed layers. This step is shown in FIG. 19.

30. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer.

31. Connect the printheads to their interconnect systems.

32. Hydrophobize the front surface of the printheads.

33. Fill the completed printheads with ink and test them. A filled nozzle is shown in FIG. 20.

It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiment without departing from the spirit or scope of the invention as broadly described. The present embodiment is, therefore, to be considered in all respects to be illustrative and not restrictive.

The presently disclosed ink jet printing technology is potentially suited to a wide range of printing systems including: color and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printers, low cost scanning printers, high speed page width printers, notebook computers with in built page width printers, portable color and monochrome printers, color and monochrome copiers, color and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic ‘minilabs’, video printers, PHOTO CD (PHOTO CD is a registered trademark of the Eastman Kodak Company) printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. However presently popular ink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption. This is approximately 100 times that required for high speed, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal ink jet applications. This leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per printhead, but is a major impediment to the fabrication of page width printheads with 19,200 nozzles.

Ideally, the ink jet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications. To meet the requirements of

digital photography, new ink jet technologies have been created. The target features include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (page width times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systems described below with differing levels of difficulty. 45 different ink jet technologies have been developed by the Assignee to give a wide range of choices for high volume manufacture. These technologies form part of separate applications assigned to the present Assignee as set out in the table under the heading Cross References to Related Applications.

The ink jet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems.

For ease of manufacture using standard process equipment, the printhead is designed to be a monolithic 0.5 micron CMOS chip with MEMS post processing. For color photographic applications, the printhead is 100 mm long, with a width which depends upon the ink jet type. The smallest printhead designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The printheads each contain 19,200 nozzles plus data and control circuitry.

Ink is supplied to the back of the printhead by injection molded plastic ink channels. The molding requires 50 micron features, which can be created using a lithographically micromachined insert in a standard injection molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The printhead is connected to the camera circuitry by tape automated bonding.

Tables of Drop-on-Demand Ink Jets

Eleven important characteristics of the fundamental operation of individual ink jet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of ink jet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of ink jet nozzle. While not all of the possible combinations result in a viable ink jet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain ink jet types have been investigated in detail. These are designated IJ01 to IJ45 which match the docket numbers in the table under the heading Cross References to Related Applications.

Other ink jet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJ01 to IJ45 examples can be made into ink jet printheads with characteristics superior to any currently available ink jet technology.

Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The IJ01 to IJ45 series are also listed in the examples column. In some cases, a print technology may be listed more than once in a table, where it shares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrix are set out in the following tables.

Description Advantages Disadvantages Examples ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) Thermal An electrothermal ♦ Large force ♦ High power ♦ Canon Bubblejet bubble heater heats the ink to generated ♦ Ink carrier 1979 Endo et al GB above boiling point, ♦ Simple limited to water patent 2,007,162 transferring significant construction ♦ Low efficiency ♦ Xerox heater-in- heat to the aqueous ♦ No moving parts ♦ High pit 1990 Hawkins et ink. A bubble ♦ Fast operation temperatures al USP 4,899,181 nucleates and quickly ♦ Small chip area required ♦ Hewlett-Packard forms, expelling the required for actuator ♦ High mechanical TIJ 1982 Vaught et ink. stress al USP 4,490,728 The efficiency of the ♦ Unusual process is low, with materials required typically less than ♦ Large drive 0.05% of the electrical transistors energy being ♦ Cavitation causes transformed into actuator failure kinetic energy of the ♦ Kogation reduces drop. bubble formation ♦ Large print heads are difficult to fabricate Piezo- A piezoelectric crystal ♦ Low power ♦ Very large area ♦ Kyser et al USP electric such as lead consumption required for actuator 3,946,398 lanthanum zirconate ♦ Many ink types ♦ Difficult to ♦ Zoltan USP (PZT) is electrically can be used integrate with 3,683,212 activated, and either ♦ Fast operation electronics ♦ 1973 Stemme expands, shears, or ♦ High efficiency ♦ High voltage USP 3,747,120 bends to apply drive transistors ♦ Epson Stylus pressure to the ink, required ♦ Tektronix ejecting drops. ♦ Full pagewidth ♦ IJ04 print heads impractical due to actuator size ♦ Requires electrical poling in high field strengths during manufacture Electro- An electric field is ♦ Low power ♦ Low maximum ♦ Seiko Epson, strictive used to activate consumption strain (approx. Usui et all JP electrostriction in ♦ Many ink types 0.01%) 253401/96 relaxor materials such can be used ♦ Large area ♦ IJ04 as lead lanthanum ♦ Low thermal required for actuator zirconate titanate expansion due to low strain (PLZT) or lead ♦ Electric field ♦ Response speed magnesium niobate strength required is marginal (˜10 (PMN). (approx. 3.5 V/μm) μs) can be generated ♦ High voltage without difficulty drive transistors ♦ Does not require required electrical poling ♦ Full pagewidth print heads impractical due to actuator size Ferro- An electric field is ♦ Low power ♦ Difficult to ♦ IJ04 electric used to induce a phase consumption integrate with transition between the ♦ Many ink types electronics antiferroelectric (AFE) can be used ♦ Unusual and ferroelectric (FE) ♦ Fast operation materials such as phase. Perovskite (<1 μs) PLZSnT are materials such as tin ♦ Relatively high required modified lead longitudinal strain ♦ Actuators require lanthanum zirconate ♦ High efficiency a large area titanate (PLZSnT) ♦ Electric field exhibit large strains of strength of around 3 up to 1% associated V/μm can be readily with the AFE to FE provided phase transition. Electro- Conductive plates are ♦ Low power ♦ Difficult to ♦ IJ02, IJ04 static plates separated by a consumption operate electrostatic compressible or fluid ♦ Many ink types devices in an dielectric (usually air). can be used aqueous Upon application of a ♦ Fast operation environment voltage, the plates ♦ The electrostatic attract each other and actuator will displace ink, causing normally need to be drop ejection. The separated from the conductive plates may ink be in a comb or ♦ Very large area honeycomb structure, required to achieve or stacked to increase high forces the surface area and ♦ High voltage therefore the force. drive transistors may be required ♦ Full pagewidth print heads are not competitive due to actuator size Electro- A strong electric field ♦ Low current ♦ High voltage ♦ 1989 Saito et al, static pull is applied to the ink, consumption required USP 4,799,068 on ink whereupon ♦ Low temperature ♦ May be damaged ♦ 1989 Miura et al, electrostatic attraction by sparks due to air USP 4,810,954 accelerates the ink breakdown ♦ Tone-jet towards the print ♦ Required field medium. strength increases as the drop size decreases ♦ High voltage drive transistors required ♦ Electrostatic field attracts dust Permanent An electromagnet ♦ Low power ♦ Complex ♦ IJ07, IJ10 magnet directly attracts a consumption fabrication electro- permanent magnet, ♦ Many ink types ♦ Permanent magnetic displacing ink and can be used magnetic material causing drop ejection. ♦ Fast operation such as Neodymium Rare earth magnets ♦ High efficiency Iron Boron (NdFeB) with a field strength ♦ Easy extension required. around 1 Tesla can be from single nozzles ♦ High local used. Examples are: to pagewidth print currents required Samarium Cobalt heads ♦ Copper (SaCo) and magnetic metalization should materials in the be used for long neodymium iron boron electromigration family (NdFeB, lifetime and low NdDyFeBNb, resistivity NdDyFeB, etc) ♦ Pigmented inks are usually infeasible ♦ Operating temperature limited to the Curie temperature (around 540 K) Soft A solenoid induced a ♦ Low power ♦ Complex ♦ IJ01, IJ05, IJ08, magnetic magnetic field in a soft consumption fabrication IJ10, IJ12, IJ14, core electro- magnetic core or yoke ♦ Many ink types ♦ Materials not IJ15, IJ17 magnetic fabricated from a can be used usually present in a ferrous material such ♦ Fast operation CMOS fab such as as electroplated iron ♦ High efficiency NiFe, CoNiFe, or alloys such as CoNiFe ♦ Easy extension CoFe are required [1], CoFe, or NiFe from single nozzles ♦ High local alloys. Typically, the the pagewidth print currents required soft magnetic material heads ♦ Copper is in two parts, which ♦ metalization should are normally held be used for long apart by a spring. electromigration When the solenoid is lifetime and low actuated, the two parts resistivity attract, displacing the ♦ Electroplating is ink. required ♦ High saturation flux density is required (2.0-2.1 T is achievable with CoNiFe [1]) Lorenz The Lorenz force ♦ Low power ♦ Force acts as a ♦ IJ06, IJ11, IJ13, force acting on a current consumption twisting motion IJ16 carrying wire in a ♦ Many ink types ♦ Typically, only a magnetic field is can be used quarter of the utilized. ♦ Fast operation solenoid length This allows the ♦ High efficiency provides force in a magnetic field to be ♦ Easy extension. useful direction supplied externally to from single nozzles ♦ High local the print head, for to pagewidth print currents required example with rare heads ♦ Copper earth permanent metalization should magnets. be used for long Only the current electromigration carrying wire need be lifetime and low fabricated on the print- resistivity head, simplifying ♦ Pigmented inks materials are usually requirements. infeasible Magneto- The actuator uses the ♦ Many ink types ♦ Force acts as a ♦ Fischenbeck, striction giant magnetostrictive can be used twisting motion USP 4,032,929 effect of materials ♦ Fast operation ♦ Unusual IJ25 such as Terfenol-D (an ♦ Easy extension materials such as alloy of terbium, from single nozzles Terfenol-D are dysprosium and iron to pagewidth print required developed at the Naval heads ♦ High local Ordnance Laboratory, ♦ High force is currents required hence Ter-Fe-NOL). available ♦ Copper For best efficiency, the metalization should actuator should be pre- be used for long stressed to approx. 8 electromigration MPa. lifetime and low resistivity ♦ Pre-stressing may be required Surface Ink under positive ♦ Low power ♦ Requires ♦ Silverbrook, EP tension pressure is held in a consumption supplementary force 0771 658 A2 and reduction nozzle by surface ♦ Simple to effect drop related patent tension. The surface construction separation applications tension of the ink is ♦ No unusual ♦ Requires special reduced below the materials required in ink surfactants bubble threshold, fabrication ♦ Speed may be causing the ink to ♦ High efficiency limited by surfactant egress from the ♦ Easy extension properties nozzle. from single nozzles to pagewidth print heads Viscosity The ink viscosity is ♦ Simple ♦ Requires ♦ Silverbrook, EP reduction locally reduced to construction supplementary force 0771 658 A2 and select which drops are ♦ No unusual to effect drop related patent to be ejected. A materials required in separation applications viscosity reduction can fabrication ♦ Requires special be achieved ♦ Easy extension ink viscosity electrothermally with from single nozzles properties most inks, but special to pagewidth print ♦ High speed is inks can be engineered heads difficult to achieve for a 100:1 viscosity ♦ Requires reduction. oscillating ink pressure ♦ A high temperature difference (typically 80 degrees) is required Acoustic An acoustic wave is ♦ Can operate ♦ Complex drive ♦ 1993 Hadimioglu generated and without a nozzle circuitry et al, EUP 550,192 focussed upon the plate ♦ Complex ♦ 1993 Elrod et al, drop ejection region. fabrication EUP 572,220 ♦ Low efficiency ♦ Poor control of drop position ♦ Poor control of drop volume Thermo- An actuator which ♦ Low power ♦ Efficient aqueous ♦ IJ03, IJ09, IJ17, elastic bend relies upon differential consumption operation requires a IJ18, IJ19, IJ20, actuator thermal expansion ♦ Many ink types thermal insulator on IJ21, IJ22, IJ23, upon Joule heating is can be used the hot side IJ24, IJ27, IJ28, used. ♦ Simple planar ♦ Corrosion IJ29, IJ30, IJ31, fabrication prevention can be IJ32, IJ33, IJ34, ♦ Small chip area difficult IJ35, IJ36, IJ37, required for each ♦ Pigmented inks IJ38, IJ39, IJ40, actuator may be infeasible, IJ41 ♦ Fast operation as pigment particles ♦ High efficiency may jam the bend ♦ CMOS actuator compatible voltages and currents ♦ Standard MEMS processes can be used ♦ Easy extension from single nozzles to pagewidth print heads High CTE A material with a very ♦ High force can ♦ Requires special ♦ IJ09, IJ17, IJ18, thermo- high coefficient of be generated material (e.g. PTFE) IJ20, IJ21, IJ22, elastic thermal expansion ♦ Three methods of ♦ Requires a PTFE IJ23, IJ24, IJ27, actuator (CTE) such as PTFE deposition are deposition process, IJ28, IJ29, IJ30, polytetrafluoroethylene under development: which is not yet IJ31, IJ42, IJ43, (PTFE) is used. As chemical vapor standard in ULSI IJ44 high CTE materials deposition (CVD), fabs are usually non- spin coating, and ♦ PTFE deposition conductive, a heater evaporation cannot be followed fabricated from a ♦ PTFE is a with high conductive material is candidate for low temperature (above incorporated. A 50 μm dielectric constant 350° C.) processing long PTFE bend insulation in ULSI ♦ Pigmented inks actuator with ♦ Very low power may be infeasible, polysilicon heater and consumption as pigment particles 15 mW power input ♦ Many ink types may jam the bend can provide 180 μN can be used actuator force and 10 μm ♦ Simple planar deflection. Actuator fabrication motions include: ♦ Small chip area Bend required for each Push actuator Buckle ♦ Fast operation Rotate ♦ High efficiency ♦ CMOS compatible voltages and currents ♦ Easy extension from single nozzles to pagewidth print heads Conductive A polymer with a high ♦ High force can ♦ Requires special ♦ IJ24 polymer coefficient of thermal be generated materials thermo- expansion (such as ♦ Very low power development (High elastic PTFE) is doped with consumption CTE conductive actuator conducting substances ♦ Many ink types polymer) to increase its can be used ♦ Requires a PTFE conductivity to about 3 ♦ Simple planar deposition process, orders of magnitude fabrication which is not yet below that of copper. ♦ Small chip area standard in ULSI The conducting required for each fabs polymer expands actuator ♦ PTFE deposition when resistively ♦ Fast operation cannot be followed heated. ♦ High efficiency with high Examples of ♦ CMOS temperature (above conducting dopants compatible voltages 350° C.) processing include: and currents ♦ Evaporation and Carbon nanotubes ♦ Easy extension CVD deposition Metal fibers from single nozzles techniques cannot Conductive polymers to pagewidth print be used such as doped heads ♦ Pigmented inks polythiophene may be infeasible, Carbon granules as pigment particles may jam the bend actuator Shape A shape memory alloy ♦ High force is ♦ Fatigue limits ♦ IJ26 memory such as TiNi (also available (stresses maximum number alloy known as Nitinol - of hundreds of MPa) of cycles Nickel Titanium alloy ♦ Large strain is ♦ Low strain (1%) developed at the Naval available (more than is required to extend Ordnance Laboratory) 3%) fatigue resistance is thermally switched ♦ High corrosion ♦ Cycle rate between its weak resistance limited by heat martensitic state and ♦ Simple removal its high stiffness construction ♦ Requires unusual austenic state. The ♦ Easy extension materials (TiNi) shape of the actuator from single nozzles ♦ The latent heat of in its martensitic state to pagewidth print transformation must is deformed relative to heads be provided the austenic shape. ♦ Low voltage ♦ High current The shape change operation operation causes ejection of a ♦ Requires pre- drop. stressing to distort the martensitic state Linear Linear magnetic ♦ Linear Magnetic ♦ Requires unusual ♦ IJ12 Magnetic actuators include the actuators can be semiconductor Actuator Linear Induction constructed with materials such as Actuator (LIA), Linear high thrust, long soft magnetic alloys Permanent Magnet travel, and high (e.g. CoNiFe) Synchronous Actuator efficiency using ♦ Some varieties (LPMSA), Linear planar also require Reluctance semiconductor permanent magnetic Synchronous Actuator fabrication materials such as (LRSA), Linear techniques Neodymium iron Switched Reluctance ♦ Long actuator boron (NdFeB) Actuator (LSRA), and travel is available ♦ Requires the Linear Stepper ♦ Medium force is complex multi- Actuator (LSA). available phase drive circuitry ♦ Low voltage ♦ High current operation operation BASIC OPERATION MODE Actuator This is the simplest ♦ Simple operation ♦ Drop repetition ♦ Thermal ink jet directly mode of operation: the ♦ No external rate is usually ♦ Piezoelectric ink pushes ink actuator directly fields required limited to around 10 jet supplies sufficient ♦ Satellite drops kHz. However, this ♦ IJ01, IJ02, IJ03, kinetic energy to expel can be avoided if is not fundamental IJ04, IJ05, IJ06, the drop. The drop drop velocity is less to the method, but is IJ07, IJ09, IJ11, must have a sufficient than 4 m/s related to the refill IJ12, IJ14, IJ16, velocity to overcome ♦ Can be efficient, method normally IJ20, IJ22, IJ23, the surface tension. depending upon the used IJ24, IJ25, IJ26, actuator used ♦ All of the drop IJ27, IJ28, IJ29, kinetic energy must IJ30, IJ31, IJ32, be provided be the IJ33, IJ34, IJ35, actuator IJ36, IJ37, IJ38, ♦ Satellite drops IJ39, IJ40, IJ41, usually form if drop IJ42, IJ43, IJ44 velocity is greater than 4.5 m/s Proximity The drops to be ♦ Very simple print ♦ Requires close ♦ Silverbrook, EP printed are selected by head fabrication can proximity between 0771 658 A2 and some manner (e.g. be used the print head and related patent thermally induced ♦ The drop the print media or applications surface tension selection means transfer roller reduction of does not need to ♦ May require two pressurized ink). provide the energy print heads printing Selected drops are required to separate alternate rows of the separated from the ink the drop from the image in the nozzle by nozzle ♦ Monolithic color contact with the print print heads are medium or a transfer difficult roller. Electro- The drops to be ♦ Very simple print ♦ Requires very ♦ Silverbrook, EP static pull printed are selected by head fabrication can high electrostatic 0771 658 A2 and on ink some manner (e.g be used field related patent thermally induced ♦ The drop ♦ Electrostatic field applications surface tension selection means for small nozzle ♦ Tone-Jet reduction of does not need to sizes is above air pressurized ink). provide the energy breakdown Selected drops are required to separate ♦ Electrostatic field separated from the ink the drop from the may attract dust in the nozzle by a nozzle strong electric field. Magnetic The drops to be ♦ Very simple print ♦ Requires ♦ Silverbrook, EP pull on ink printed are selected by head fabrication can magnetic ink 0771 658 A2 and some manner (e.g. be used ♦ Ink colors other related patent thermally induced ♦ The drop than black are applications surface tension selection means difficult reduction of does not need to ♦ Requires very pressurized ink). provide the energy high magnetic fields Selected drops are required to separate separated from the ink the drop from the in the nozzle by a nozzle strong magnetic field acting on the magnetic ink. Shutter The actuator moves a ♦ High speed (>50 ♦ Moving parts are ♦ IJ13, IJ17, IJ21 shutter to block ink kHz) operation can required flow to the nozzle. The be achieved due to ♦ Requires ink ink pressure is pulsed reduced refill time pressure modulator at a multiple of the ♦ Drop timing can ♦ Friction and wear drop ejection be very accurate must be considered frequency. ♦ The actuator ♦ Striction is energy can be very possible low Shuttered The actuator moves a ♦ Actuators with ♦ Moving parts are ♦ IJ08, IJ15, IJ18, grill shutter to block ink small travel can be required IJ19 flow through a grill to used ♦ Requires ink the nozzle. The shutter ♦ Actuators with pressure modulator movement need only small force can be ♦ Friction and wear be equal to the width used must be considered of the grill holes. ♦ High speed (>50 ♦ Striction is kHz) operation can possible be achieved Pulsed A pulsed magnetic ♦ Extremely low ♦ Requires an ♦ IJ10 magnetic field attracts an ‘ink energy operation is external pulsed pull on ink pusher’ at the drop possible magnetic field pusher ejection frequency. An ♦ No heat ♦ Requires special actuator controls a dissipation materials for both catch, which prevents problems the actuator and the the ink pusher from ink pusher moving when a drop is ♦ Complex not to be ejected. construction AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) None The actuator directly ♦ Simplicity of ♦ Drop ejection ♦ Most ink jets, fires the ink drop, and construction energy must be including there is no external ♦ Simplicity of supplied by piezoelectric and field or other operation individual nozzle thermal bubble. mechanism required. ♦ Small physical actuator ♦ IJ01, IJ02, IJ03, size IJ04, IJ05, IJ07, IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23, IJ24, IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Oscillating The ink pressure ♦ Oscillating ink ♦ Requires external ♦ Silverbrook, EP ink pressure oscillates, providing pressure can provide ink pressure 0771 658 A2 and (including much of the drop a refill pulse, oscillator related patent acoustic ejection energy. The allowing higher ♦ Ink pressure applications stimu- actuator selects which operating speed phase and amplitude ♦ IJ08, IJ13, IJ15, lation) drops are to be fired ♦ The actuators must be carefully IJ17, IJ18, IJ19, by selectively may operate with controlled IJ21 blocking or enabling much lower energy ♦ Acoustic nozzles. The ink ♦ Acoustic lenses reflections in the ink pressure oscillation can be used to focus chamber must be may be achieved by the sound on the designed for vibrating the print nozzles head, or preferably by an actuator in the ink supply. Media The print head is ♦ Low power ♦ Precision ♦ Silverbrook, EP proximity placed in close High accuracy assembly required 0771 658 A2 and proximity to the print ♦ Simple print head ♦ Paper fibers may related patent medium. Selected construction cause problems applications drops protrude from ♦ Cannot print on the print head further rough substrates than unselected drops, and contact the print medium. The drop soaks into the medium fast enough to cause drop separation. Transfer Drops are printed to a ♦ High accuracy ♦ Bulky ♦ Silverbrook, EP roller transfer roller instead ♦ Wide range of ♦ Expensive 0771 658 A2 and of straight to the print print substrates can ♦ Complex related patent medium. A transfer be used construction applications roller can also be used ♦ Ink can be dried ♦ Tektronix hot for proximity drop on the transfer roller melt piezoelectric separation. ink jet ♦ Any of the IJ series Electro- An electric field is ♦ Low power ♦ Field strength ♦ Silverbrook, EP static used to accelerate ♦ Simple print head required for 0771 658 A2 and selected drops towards construction separation of small related patent the print medium. drops is near or applications above air ♦ Tone-Jet breakdown Direct A magnetic field is ♦ Low power ♦ Requires ♦ Silverbrook, EP magnetic used to accelerate ♦ Simple print head magnetic ink 0771 658 A2 and field selected drops of construction ♦ Requires strong related patent magnetic ink towards magnetic field applications the print medium. Cross The print head is ♦ Does not require ♦ Requires external ♦ IJ06, IJ16 magnetic placed in a constant magnetic materials magnet field magnetic field. The to be integrated in ♦ Current densities Lorenz force in a the print head may be high, current carrying wire manufacturing resulting in is used to move the process electromigration actuator. problems Pulsed A pulsed magnetic ♦ Very low power ♦ Complex print ♦ IJI0 magnetic field is used to operation is possible head construction field cyclically attract a ♦ Small print head ♦ Magnetic paddle, which pushes size materials required in on the ink. A small print head actuator moves a catch, which selectively prevents the paddle from moving. ACTUATOR AMPLIFICATION OR MODIFICATION METHOD None No actuator ♦ Operational ♦ Many actuator ♦ Thermal Bubble mechanical simplicity mechanisms have Ink jet amplification is used. insufficient travel, ♦ IJ01, IJ02, IJ06, The actuator directly or insufficient force, IJ07, IJ16, IJ25, drives the drop to efficiently drive IJ26 ejection process. the drop ejection process Differential An actuator material ♦ Provides greater ♦ High stresses are ♦ Piezoelectric expansion expands more on one travel in a reduced involved ♦ IJ03, IJ09, IJ17, bend side than on the other. print head area ♦ Care must be IJ18, IJ19, IJ20, actuator The expansion may be taken that the IJ21, IJ22, IJ23, thermal, piezoelectric, materials do not IJ24, IJ27, IJ29, magnetostrictive, or delaminate IJ30, IJ31, IJ32, other mechanism. The ♦ Residual bend IJ33, IJ34, IJ35, bend actuator converts resulting from high IJ36, IJ37, IJ38, a high force low travel temperature or high IJ39, IJ42, IJ43, actuator mechanism to stress during IJ44 high travel, lower formation force mechanism. Transient A trilayer bend ♦ Very good ♦ High stresses are ♦ IJ40, IJ41 bend actuator where the two temperature stability involved actuator outside layers are ♦ High speed, as a ♦ Care must be identical. This cancels new drop can be taken that the bend due to ambient fired before heat materials do not temperature and dissipates delaminate residual stress. The ♦ Cancels residual. actuator only responds stress of formation to transient heating of one side or the other. Reverse The actuator loads a ♦ Better coupling ♦ Fabrication ♦ IJ05, IJ11 spring spring. When the to the ink complexity actuator is turned off, ♦ High stress in the the spring releases. spring This can reverse the force/distance curve of the actuator to make it compatible with the force/time requirements of the drop ejection Actuator A series of thin ♦ Increased travel ♦ Increased ♦ Some stack actuators are stacked. ♦ Reduced drive fabrication piezoelectric ink jets This can be voltage complexity ♦ IJ04 appropriate where ♦ Increased actuators require high possibility of short electric field strength, circuits due to such as electrostatic pinholes and piezoelectric actuators. Multiple Multiple smaller ♦ Increases the ♦ Actuator forces ♦ IJ12, IJ13, IJ18, actuators actuators are used force available from may not add IJ20, IJ22, IJ28, simultaneously to an actuator linearly, reducing IJ42, IJ43 move the ink. Each ♦ Multiple efficiency actuator need provide actuators can be only a portion of the positioned to control force required. ink flow accurately Linear A linear spring is used ♦ Matches low ♦ Requires print ♦ IJ15 Spring to transform a motion travel actuator with head area for the with small travel and higher travel spring high force into a requirements longer travel, lower ♦ Non-contact force motion. method of motion transformation Coiled A bend actuator is ♦ Increases travel ♦ Generally ♦ IJ17, IJ21, IJ34, actuator coiled to provide ♦ Reduces chip restricted to planar IJ35 greater travel in a area implementations reduced chip area. ♦ Planar due to extreme implementations are fabrication difficulty relatively easy to in other orientations. fabricate. Flexure A bend actuator has a ♦ Simple means of ♦ Care must be ♦ IJ10, IJ19, IJ33 bend small region near the increasing travel of taken not to exceed actuator fixture point, which a bend actuator the elastic limit in flexes much more the flexure area readily than the ♦ Stress remainder of the distribution is very actuator. The actuator uneven flexing is effectively ♦ Difficult to converted from an accurately model even coiling to an with finite element angular bend, resulting analysis in greater travel of the actuator tip. Catch The actuator controls a ♦ Very low ♦ Complex ♦ IJ10 small catch. The catch actuator energy construction either enables or ♦ Very small ♦ Requires external disables movement of actuator size force an ink pusher that is ♦ Unsuitable for controlled in a bulk pigmented inks manner. Gears Gears can be used to ♦ Low force, low ♦ Moving parts are ♦ IJ13 increase travel at the travel actuators can required expense of duration. be used ♦ Several actuator Circular gears, rack ♦ Can be fabricated cycles are required and pinion, ratchets, using standard ♦ More complex and other gearing surface MEMS drive electronics methods can be used. processes ♦ Complex construction ♦ Friction, friction, and wear are possible Buckle plate A buckle plate can be ♦ Very fast ♦ Must stay within ♦ S. Hirata et al, used to change a slow movement elastic limits of the “An Ink-jet Head actuator into a fast achievable materials for long Using Diaphragm motion. It can also device life Microactuator”, convert a high force, ♦ High stresses Proc. IEEE MEMS, low travel actuator involved Feb. 1996, pp 418- into a high travel, ♦ Generally high 423. medium force motion. power requirement ♦ IJ18, IJ27 Tapered A tapered magnetic ♦ Linearizes the ♦ Complex ♦ IJ14 magnetic pole can increase magnetic construction pole travel at the expense force/distance curve of force. Lever A lever and fulcrum is ♦ Matches low ♦ High stress ♦ IJ32, IJ36, IJ37 used to transform a travel actuator with around the fulcrum motion with small higher travel travel and high force requirements into a motion with ♦ Fulcrum area has longer travel and no linear movement, lower force. The lever and can be used for can also reverse the a fluid seal direction of travel. Rotary The actuator is ♦ High mechanical ♦ Complex ♦ IJ28 impeller connected to a rotary advantage construction impeller. A small ♦ The ratio of force ♦ Unsuitable for angular deflection of to travel of the pigmented inks the actuator results in actuator can be a rotation of the matched to the impeller vanes, which nozzle requirements push the ink against by varying the stationary vanes and number of impeller out of the nozzle. vanes Acoustic A refractive or ♦ No moving parts ♦ Large area ♦ 1993 Hadimioglu lens diffractive (e.g. zone required et al, EUP 550,192 plate) acoustic lens is ♦ Only relevant for ♦ 1993 Elrod et al, used to concentrate acoustic ink jets EUP 572,220 sound waves. Sharp A sharp point is used ♦ Simple ♦ Difficult to ♦ Tonejet conductive to concentrate an construction fabricate using point electrostatic field. standard VLSI processes for a surface ejecting ink- jet ♦ Only relevant for electrostatic ink jets ACTUATOR MOTION Volume The volume of the ♦ Simple ♦ High energy is ♦ Hewlett-Packard expansion actuator changes construction in the typically required to Thermal Ink jet pushing the ink in all case of thermal ink achieve volume ♦ Canon Bubblejet directions. jet expansion. This leads to thermal. stress, cavitation, and kogation in thermal ink jet implementations Linear, The actuator moves in ♦ Efficient ♦ High fabrication ♦ IJ01, IJ02, IJ04, normal to a direction normal to coupling to ink complexity may be IJ07, IJ11, IJ14 chip surface the print head surface. drops ejected required to achieve The nozzle is typically normal to the perpendicular in the line of surface motion movement. Parallel to The actuator moves ♦ Suitable for ♦ Fabrication ♦ IJ12, IJ13, IJ15, chip surface parallel to the print planar fabrication complexity IJ33, IJ34, IJ35, head surface. Drop ♦ Friction IJ36 ejection may still be ♦ Striction normal to the surface. Membrane An actuator with a ♦ The effective ♦ Fabrication ♦ 1982 Hawkins push high force but small area of the actuator complexity USP 4,459,601 area is used to push a becomes the ♦ Actuator size stiff membrane that is membrane area ♦ Difficulty of in contact with the ink. integration in a VLSI process Rotary The actuator causes ♦ Rotary levers ♦ Device ♦ IJ05, IJ08, IJ13, the rotation of some may be used to complexity IJ28 element, such a grill or increase travel ♦ May have impeller ♦ Small chip area friction at a pivot requirements point Bend The actuator bends ♦ A very small ♦ Requires the ♦ 1970 Kyser et al when energized. This change in actuator to be made USP 3,946,398 may be due to dimensions can be from at least two ♦ 1973 Stemme differential thermal converted to a large distinct layers, or to USP 3,747,120 expansion, motion. have a thermal ♦ IJ03, IJ09, IJ10, piezoelectric difference across the IJ19, IJ23, IJ24, expansion, actuator IJ25, IJ29, IJ30, magnetostriction, or IJ31, IJ33, IJ34, other form of relative IJ35 dimensional change. Swivel The actuator swivels ♦ Allows operation ♦ Inefficient ♦ IJ06 around a central pivot. where the net linear coupling to the ink This motion is suitable force on the paddle motion where there are is zero opposite forces ♦ Small chip area applied to opposite requirements sides of the paddle, e.g. Lorenz force. Straighten The actuator is ♦ Can be used with ♦ Requires careful ♦ IJ26, IJ32 normally bent, and shape memory balance of stresses straightens when alloys where the to ensure that the energized. austenic phase is quiescent bend is planar accurate Double The actuator bends in ♦ One actuator can ♦ Difficult to make ♦ IJ36, IJ37, IJ38 bend one direction when be used to power the drops ejected by one element is two nozzles. both bend directions energized, and bends ♦ Reduced chip identical. the other way when size. ♦ A small another element is ♦ Not sensitive to efficiency loss energized. ambient temperature compared to equivalent single bend actuators. Shear Energizing the ♦ Can increase the ♦ Not readily ♦ 1985 Fishbeck actuator causes a shear effective travel of applicable to other USP 4,584,590 motion in the actuator piezoelectric actuator material. actuators mechanisms Radial The actuator squeezes ♦ Relatively easy ♦ High force ♦ 1970 Zoltan USP constriction an ink reservoir, to fabricate single required 3,683,212 forcing ink from a nozzles from glass ♦ Inefficient constricted nozzle. tubing as ♦ Difficult to macroscopic integrate with VLSI structures processes Coil/uncoil A coiled actuator ♦ Easy to fabricate ♦ Difficult to ♦ IJ17, IJ21, IJ34, uncoils or coils more as a planar VLSI fabricate for non- IJ35 tightly. The motion of process planar devices the free end of the ♦ Small area ♦ Poor out-of-plane actuator ejects the ink. required, therefore stiffness low cost Bow The actuator bows (or ♦ Can increase the ♦ Maximum travel ♦ IJ16, IJ18, IJ27 buckles) in the middle speed of travel is constrained where energized. ♦ Mechanically ♦ High force rigid required Push-Pull Two actuators control ♦ The structure is ♦ Not readily ♦ IJ18 a shutter. One actuator pinned at both ends, suitable for ink jets pulls the shutter, and so has a high out-of- which directly push the other pushes it. plane rigidity the ink Curl A set of actuators curl ♦ Good fluid flow ♦ Design ♦ IJ20, IJ42 inwards inwards to reduce the to the region behind complexity volume of ink that the actuator they enclose. increases efficiency Curl A set of actuators curl ♦ Relatively simple ♦ Relatively large ♦ IJ43 outwards outwards, pressurizing construction chip area ink in a chamber surrounding the actuators, and expelling ink from a nozzle in the chamber. Iris Multiple vanes enclose ♦ High efficiency ♦ High fabrication ♦ IJ22 a volume of ink. These ♦ Small chip area complexity simultaneously rotate, ♦ Not suitable for reducing the volume pigmented inks between the vanes. Acoustic The actuator vibrates ♦ The actuator can ♦ Large area ♦ 1993 Hadimioglu vibration at a high frequency. be physically distant required for et al, EUP 550,192 from the ink efficient operation ♦ 1993 Elrod et al, at useful frequencies EUP 572,220 ♦ Acoustic coupling and crosstalk ♦ Complex drive circuitry ♦ Poor control of drop volume and position None In various ink jet ♦ No moving parts ♦ Various other ♦ Silverbrook, EP designs the actuator tradeoffs are 0771 658 A2 and does not move. required to related patent eliminate moving applications parts ♦ Tone-jet NOZZLE REFILL METHOD Surface This is the normal way ♦ Fabrication ♦ Low speed ♦ Thermal ink jet tension that ink jets are simplicity ♦ Surface tension ♦ Piezoelectric ink refilled. After the ♦ Operational force relatively jet actuator is energized, simplicity small compared to ♦ IJ01-IJ07, IJ10- it typically returns actuator force IJ14, IJ16, IJ20, rapidly to its normal ♦ Long refill time IJ22-IJ45 position. This rapid usually dominates return sucks in air the total repetition through the nozzle rate opening. The ink surface tension at the nozzle then exerts a small force restoring the meniscus to a minimum area. This force refills the nozzle. Shuttered Ink to the nozzle ♦ High speed ♦ Requires ♦ IJ08, IJ13, IJ15, oscillating chamber is provided at ♦ Low actuator common ink IJ17, IJ18, IJ19, ink pressure a pressure that energy, as the pressure oscillator IJ21 oscillates at twice the actuator need only ♦ May not be drop ejection open or close the suitable for frequency. When a shutter, instead of pigmented inks drop is to be ejected, ejecting the ink drop the shutter is opened for 3 half cycles: drop ejection, actuator return, and refill. The shutter is then closed to prevent the nozzle chamber emptying during the next negative pressure cycle. Refill After the main ♦ High speed, as ♦ Requires two ♦ IJ09 actuator actuator has ejected a the nozzle is independent drop a second (refill) actively refilled actuators per nozzle actuator is energized. The refill actuator pushes ink into the nozzle chamber. The refill actuator returns slowly, to prevent its return from emptying the chamber again. Positive ink The ink is held a slight ♦ High refill rate, ♦ Surface spill ♦ Silverbrook, EP pressure positive pressure. therefore a high must be prevented 0771 658 A2 and After the ink drop is drop repetition rate ♦ Highly related patent ejected, the nozzle is possible hydrophobic print applications chamber fills quickly head surfaces are ♦ Alternative for:, as surface tension and required IJ01-IJ07, IJ10-IJ14, ink pressure both IJ16, IJ20, IJ22-IJ45 operate to refill the nozzle. METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Long inlet The ink inlet channel ♦ Design simplicity ♦ Restricts refill ♦ Thermal ink jet channel to the nozzle chamber ♦ Operational rate ♦ Piezoelectric ink is made long and simplicity ♦ May result in a jet relatively narrow, ♦ Reduces relatively large chip ♦ IJ42, IJ43 relying on viscous crosstalk area drag to reduce inlet ♦ Only partially back-flow. effective Positive ink The ink is under a ♦ Drop selection ♦ Requires a ♦ Silverbrook, EP pressure positive pressure, so and separation method (such as a 0771 658 A2 and that in the quiescent forces can be nozzle rim or related patent state some of the ink reduced effective applications drop already protrudes ♦ Fast refill time hydrophobizing, or ♦ Possible from the nozzle. both) to prevent operation of the This reduces the flooding of the following: IJ01- pressure in the nozzle ejection surface of IJ07, IJ09-IJ12, chamber which is the print head. IJ14, IJ16, IJ20, required to eject a IJ22, IJ23-IJ34, certain volume of ink. IJ36-IJ41,IJ44 The reduction in chamber pressure results in a reduction in ink pushed out through the inlet. Baffle One or more baffles ♦ The refill rate is ♦ Design ♦ HP Thermal ink are placed in the inlet not as restricted as complexity Jet ink flow. When the the long inlet ♦ May increase ♦ Tektronix actuator is energized, method. fabrication piezoelectric ink jet the rapid ink ♦ Reduces complexity (e.g. movement creates. crosstalk Tektronix hot melt eddies which restrict Piezoelectric print the flow through the heads). inlet. The slower refill process is unrestricted, and does not result in eddies. Flexible flap In this method recently ♦ Significantly ♦ Not applicable to ♦ Canon restricts disclosed by Canon, reduces back-flow most ink jet inlet the expanding actuator for edge-shooter configurations (bubble) pushes on a thermal ink jet ♦ Increased flexible flap that devices fabrication restricts the inlet. complexity ♦ Inelastic deformation of polymer flap results in creep over extended use METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Inlet filter A filter is located ♦ Additional ♦ Restricts refill ♦ IJ04, IJ12, IJ24, between the ink inlet advantage of ink rate IJ27, IJ29, IJ30 and the nozzle filtration ♦ May result in chamber. The filter ♦ Ink filter may be complex has a multitude of fabricated with no construction small holes for slots, additional process restricting ink flow. steps The filter also removes particles which may block the nozzle. Small inlet The ink inlet channel ♦ Design simplicity ♦ Restricts refill ♦ IJ02, IJ37, IJ44 compared to the nozzle chamber rate to nozzle has a substantially ♦ May result in a small or cross section relatively large chip than that of the nozzle, area resulting in easier ink ♦ Only partially egress out of the effective nozzle than out of the inlet. Inlet shutter A secondary actuator ♦ Increases speed ♦ Requires separate ♦ IJ09 controls the position of of the ink-jet print refill actuator and a shutter, closing off head operation drive circuit the ink inlet when the main actuator is energized. The inlet is The method avoids the ♦ Back-flow ♦ Requires careful ♦ IJ01, IJ03, IJ05, located problem of inlet back- problem is design to minimize IJ06, IJ07, IJ10, behind the flow by arranging the eliminated the negative IJ11, IJ14, IJ16, ink-pushing ink-pushing surface of pressure behind the IJ22, IJ23, IJ25, surface the actuator between paddle IJ28, IJ31, IJ32, the inlet and the IJ33, IJ34, IJ35, nozzle. IJ36, IJ39, IJ40, IJ41 Part of the The actuator and a ♦ Significant ♦ Small increase in ♦ IJ07, IJ20, IJ26, actuator wall of the ink reductions in back- fabrication IJ38 moves to chamber are arranged flow can be complexity shut off the so that the motion of achieved inlet the actuator closes off ♦ Compact designs the inlet. possible Nozzle In some configurations ♦ Ink back-flow ♦ None related to ♦ Silverbrook, EP actuator of ink jet, there is no problem is ink back-flow on 0771 658 A2 and does not expansion or eliminated actuation related patent result in ink movement of an applications back-flow actuator which may ♦ Valve-jet cause ink back-flow ♦ Tone-jet through the inlet. NOZZLE CLEARING METHOD Normal All of the nozzles are ♦ No added ♦ May not be ♦ Most ink jet nozzle firing fired periodically, complexity on the sufficient to systems before the ink has a print head displace dried ink ♦ IJ01, IJ02, IJ03, chance to dry. When IJ04, IJ05, IJ06, not in use the nozzles IJ07, IJ09, IJ10, are sealed (capped) IJ11, IJ12, IJ14, against air. IJ16, IJ20, IJ22, The nozzle firing is IJ23, IJ24, IJ25, usually performed IJ26, IJ27, IJ28, during a special IJ29, IJ30, IJ31, clearing cycle, after IJ32, IJ33, IJ34, first moving the print IJ36, IJ37, IJ38, head to a cleaning IJ39, IJ40, IJ41, station. IJ42, IJ43, IJ44,, IJ45 Extra In systems which heat ♦ Can be highly ♦ Requires higher ♦ Silverbrook, EP power to the ink, but do not boil effective if the drive voltage for 0771 658 A2 and ink heater it under normal heater is adjacent to clearing related patent situations, nozzle the nozzle ♦ May require applications clearing can be larger drive achieved by over- transistors powering the heater and boiling ink at the nozzle. Rapid The actuator is fired in ♦ Does not require ♦ Effectiveness ♦ May be used succession rapid succession. In extra drive circuits depends with: IJ01, IJ02, of actuator some configurations, on the print head substantially upon IJ03, IJ04, IJ05, pulses this may cause heat ♦ Can be readily the configuration of IJ06, IJ07, IJ09, build-up at the nozzle controlled and the ink jet nozzle IJ10, IJ11, IJ14, which boils the ink, initiated by digital IJ16, IJ20, IJ22, clearing the nozzle. In logic IJ23, IJ24, IJ25, other situations, it may IJ27, IJ28, IJ29, cause sufficient IJ30, IJ31, IJ32, vibrations to dislodge IJ33, IJ34, IJ36, clogged nozzles. IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44, IJ45 Extra Where an actuator is ♦ A simple ♦ Not suitable ♦ May be used power to not normally driven to solution where where there is a with: IJ03, IJ09, ink pushing the limit of its motion, applicable hard limit to IJ16, IJ20, IJ23, actuator nozzle clearing may be actuator movement IJ24, IJ25, IJ27, assisted by providing IJ29, IJ30, IJ31, an enhanced drive IJ32, IJ39, IJ40, signal to the actuator. IJ41, IJ42, IJ43, IJ44, IJ45 Acoustic An ultrasonic wave is ♦ A high nozzle ♦ High ♦ IJ08, IJ13, IJ15, resonance applied to the ink clearing capability implementation cost IJ17, IJ18, IJ19, chamber. This wave is can be achieved if system does not IJ21 of an appropriate ♦ May be already include an amplitude and implemented at very acoustic actuator frequency to cause low cost in systems sufficient force at the which already nozzle to clear include acoustic blockages. This is actuators easiest to achieve if the ultrasonic wave is at a resonant frequency of the ink cavity. Nozzle A microfabricated ♦ Can clear ♦ Accurate ♦ Silverbrook, EP clearing plate is pushed against severely clogged mechanical 0771 658 A2 and plate the nozzles. The plate nozzles alignment is related patent has a post for every required applications nozzle. A post moves ♦ Moving parts are through each nozzle, required displacing dried ink. ♦ There is risk of damage to the nozzles ♦ Accurate fabrication is required Ink The pressure of the ink ♦ May be effective ♦ Requires ♦ May be used pressure is temporarily where other pressure pump or with all IJ series ink pulse increased so that ink methods cannot be other pressure jets streams from all of the used actuator nozzles. This may be ♦ Expensive used in conjunction ♦ Wasteful of ink with actuator energizing. Print head A flexible ‘blade’ is ♦ Effective for ♦ Difficult to use if ♦ Many ink jet wiper wiped across the print planar print head print head surface is systems head surface. The surfaces non-planar or very blade is usually ♦ Low cost fragile fabricated from a ♦ Requires flexible polymer, e.g. mechanical parts rubber or synthetic ♦ Blade can wear elastomer. out in high volume print systems Separate A separate heater is ♦ Can he effective ♦ Fabrication ♦ Can be used with ink boiling provided at the nozzle where other nozzle complexity many IJ series ink heater although the normal clearing methods jets drop e-ection cannot be used mechanism does not ♦ Can be require it. The heaters implemented at no do not require. additional cost in individual drive some ink jet circuits, as many configurations nozzles. can be cleared simultaneously, and no imaging is required. NOZZLE PLATE CONSTRUCTION Electro- A nozzle plate is ♦ Fabrication ♦ High ♦ Hewlett Packard formed separately fabricated simplicity temperatures and Thermal Ink jet nickel from electroformed pressures are nickel, and bonded to required to bond the print head chip. nozzle plate ♦ Minimum thickness constraints ♦ Differential thermal expansion Laser Individual nozzle ♦ No masks ♦ Each hole must ♦ Canon Bubblejet ablated or holes are ablated by an required be individually ♦ 1988 Sercel et drilled intense UV laser in a ♦ Can be quite fast formed al., SPIE, Vol. 998 polymer nozzle plate, which is ♦ Some control ♦ Special Excimer Beam typically a polymer over nozzle profile equipment required Applications, pp. such as polyimide or is possible ♦ Slow where there 76-83 polysulphone ♦ Equipment are many thousands ♦ 1993 Watanabe required is relatively of nozzles per print et al., USP low cost head 5,208,604 ♦ May produce thin burrs at exit holes Silicon A separate nozzle ♦ High accuracy is ♦ Two part ♦ K. Bean, IEEE micro- plate is attainable construction Transactions on machined micromachined from ♦ High cost Electron Devices, single crystal silicon, ♦ Requires Vol. ED-25, No. 10, and bonded to the precision alignment 1978, pp 1185-1195 print head wafer. ♦ Nozzles may be ♦ Xerox 1990 clogged by adhesive Hawkins et al., USP 4,899,181 Glass Fine glass capillaries ♦ No expensive ♦ Very small ♦ 1970 Zoltan USP capillaries are drawn from glass equipment required nozzle sizes are 3,683,212 tubing. This method ♦ Simple to make difficult to form has been used for single nozzles ♦ Not suited for making individual mass production nozzles, but is difficult to use for bulk manufacturing of print heads with thousands of nozzles. Monolithic, The nozzle plate is ♦ High accuracy ♦ Requires ♦ Silverbrook, EP surface deposited as a layer (<1 μm) sacrificial layer 0771 658 A2 and micro- using standard VLSI ♦ Monolithic under the nozzle related patent machined deposition techniques. ♦ Low cost plate to form the applications using VLSI Nozzles are etched in ♦ Existing nozzle chamber ♦ IJ01, IJ02, IJ04, litho- the nozzle plate using processes can be ♦ Surface may be IJ11, IJ12, IJ17, graphic VLSI lithography and used fragile to the touch IJ18, IJ20, IJ22, processes etching. IJ24, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Monolithic, The nozzle plate is a ♦ High accuracy ♦ Requires long ♦ IJ03, IJ05, IJ06, etched buried etch stop in the (<1 μm) etch times IJ07, IJ08, IJ09, through wafer. Nozzle ♦ Monolithic ♦ Requires a IJ10, IJ13, IJ14, substrate chambers are etched in ♦ Low cost support wafer IJ15, IJ16, IJ19, the front of the wafer, ♦ No differential IJ21, IJ23, IJ25, and the wafer is expansion IJ26 thinned from the back side. Nozzles are then etched in the etch stop layer. No nozzle Various methods have ♦ No nozzles to ♦ Difficult to ♦ Ricoh 1995 plate been tried to eliminate become clogged control drop Sekiya et al USP the nozzles entirely, to position accurately 5,412,413 prevent nozzle ♦ Crosstalk ♦ 1993 Hadimioglu clogging. These problems et al EUP 550,192 include thermal bubble ♦ 1993 Elrod et al mechanisms and EUP 572,220 acoustic lens mechanisms Trough Each drop ejector has ♦ Reduced ♦ Drop firing ♦ IJ35 a trough through manufacturing direction is sensitive which a paddle moves. complexity to wicking. There is no nozzle ♦ Monolithic plate. Nozzle slit The elimination of ♦ No nozzles to ♦ Difficult to ♦ 1989 Saito et al instead of nozzle holes and become clogged control drop USP 4,799,068 individual replacement by a slit position accurately nozzles encompassing many ♦ Crosstalk actuator positions problems reduces nozzle clogging, but increases, crosstalk due to ink surface waves DROP EJECTION DIRECTION Edge Ink flow is along the ♦ Simple ♦ Nozzles limited ♦ Canon Bubblejet (‘edge surface of the chip, construction to edge 1979 Endo et al GB shooter’) and ink drops are ♦ No silicon ♦ High resolution patent 2,007,162 ejected from the chip etching required is difficult ♦ Xerox heater-in- edge. ♦ Good heat ♦ Fast color pit 1990 Hawkins et sinking via substrate printing requires al USP 4,899,181 ♦ Mechanically one print head per ♦ Tone-jet strong color ♦ Ease of chip handing Surface Ink flow is along the ♦ No bulk silicon ♦ Maximum ink ♦ Hewlett-Packard (‘roof surface of the chip, etching required flow is severely TIJ 1982 Vaught et shooter’) and ink drops are ♦ Silicon can make restricted al USP 4,490,728 ejected from the chip an effective heat ♦ IJ02, IJ11, IJ12, surface, normal to the sink IJ20, IJ22 plane of the chip. ♦ Mechanical strength Through Ink flow is through the ♦ High ink flow ♦ Requires bulk ♦ Silverbrook, EP chip, chip, and ink drops are ♦ Suitable for silicon etching 0771 658 A2 and forward ejected from the front pagewidth print related patent (‘up surface of the chip. heads applications shooter’) ♦ High nozzle ♦ IJ04, IJ17, IJ18, packing density IJ24, IJ27-IJ45 therefore low manufacturing cost Through Ink flow is through the ♦ High ink flow ♦ Requires wafer ♦ IJ01, IJ03, IJ05, chip, chip, and ink drops are ♦ Suitable for thinning IJ06, IJ07, IJ08, reverse ejected from the rear pagewidth print ♦ Requires special IJ09, IJ10, IJ13, (‘down surface of the chip. heads handling during IJ14, IJ15, IJ16, shooter’) ♦ High nozzle manufacture IJ19, IJ21, IJ23, packing density IJ25, IJ26 therefore low manufacturing cost Through Ink flow is through the ♦ Suitable for ♦ Pagewidth print ♦ Epson Stylus actuator actuator, which is not piezoelectric print heads require ♦ Tektronix hot fabricated as part of heads several thousand melt piezoelectric the same substrate as connections to drive ink jets the drive transistors. circuits ♦ Cannot be manufactured in standard CMOS fabs ♦ Complex assembly required INK TYPE Aqueous, Water based ink which ♦ Environmentally ♦ Slow drying ♦ Most existing ink dye typically contains: friendly ♦ Corrosive jets water, dye, surfactant, ♦ No odor ♦ Bleeds on paper ♦ All IJ series ink humectant, and ♦ May jets biocide. strikethrough ♦ Silverbrook, EP Modern ink dyes have ♦ Cookies paper 0771 658 A2 and high water-fastness, related patent light fastness applications Aqueous, Water based ink which ♦ Environmentally ♦ Slow drying ♦ IJ02, IJ04, IJ21, pigment typically contains friendly ♦ Corrosive IJ26, IJ27, IJ30 water, pigment, ♦ No odor ♦ Pigment may ♦ Silverbrook, EP surfactant, humectant, ♦ Reduced bleed clog nozzles 0771 658 A2 and and biocide. ♦ Reduced wicking ♦ Pigment may related patent Pigments have an ♦ Reduced clog actuator applications advantage in reduced strikethrough mechanisms ♦ Piezoelectric ink- bleed, wicking and ♦ Cockles paper jets strikethrough. ♦ Thermal ink jets (with significant restrictions) Methyl MEK is a highly ♦ Very fast drying ♦ Odorous ♦ All IJ series ink Ethyl volatile solvent used ♦ Prints on various ♦ Flammable jets Ketone for industrial printing substrates such as (MEK) on difficult surfaces metals and plastics such as aluminum cans. Alcohol Alcohol based inks ♦ Fast drying ♦ Slight odor ♦ All IJ series ink (ethanol, 2- can be used where the ♦ Operates at sub- ♦ Flammable jets butanol, printer must operate at freezing and others) temperatures below temperatures the freezing point of ♦ Reduced paper water. An example of cockle this is in-camera ♦ Low cost consumer photographic printing. Phase The ink is solid at ♦ No drying time- ♦ High viscosity ♦ Tektronix hot change room temperature, and ink instantly freezes ♦ Printed ink melt piezoelectric (hot melt) is melted in the print on the print medium typically has a ink jets head before jetting. ♦ Almost any print ‘waxy’ feel ♦ 1989 Nowak Hot melt inks are medium can be used ♦ Printed pages USP 4,820,346 usually wax based, ♦ No paper cockle may ‘block’ ♦ All IJ series ink with a melting point occurs ♦ Ink temperature jets around 80° C. After ♦ No wicking may be above the jetting the ink freezes occurs curie point of almost instantly upon ♦ No bleed occurs permanent magnets contacting the print ♦ No strikethrough ♦ Ink heaters medium or a transfer occurs consume power roller. ♦ Long warm-up time Oil Oil based inks are ♦ High solubility ♦ High viscosity: ♦ All IJ series ink extensively used in medium for some this is a significant jets offset printing. They dyes limitation for use in have advantages in ♦ Does not cockle ink jets, which improved paper usually require a characteristics on ♦ Does not wick low viscosity. Some paper (especially no through paper short chain and wicking or cockle). multi-branched oils Oil soluble dies and have a sufficiently pigments are required. low viscosity. ♦ Slow drying Micro- A microemulsion is a ♦ Stops ink bleed ♦ Viscosity higher ♦ All IJ series ink emulsion stable, self forming ♦ High dye than water jets emulsion of oil, water, solubility ♦ Cost is slightly and surfactant. The ♦ Water, oil, and higher than water characteristic drop size amphiphilic soluble based ink is less than 100 nm, dies can be used ♦ High surfactant and is determined by ♦ Can stabilize concentration the preferred curvature pigment required (around of the surfactant. suspensions 5%) 

What is claimed is:
 1. A method of ejecting ink from an ink jet printing nozzle apparatus, the apparatus comprising: (a) a nozzle chamber having an ink ejection port and being in fluid connection with an ink chamber; (b) an ink ejection device having one surface in fluid communication with ink in said nozzle chamber; (c) a recoil device connected to said ink ejection device; and (d) an actuator device connected to the ink ejection device;  wherein said method comprises the steps of: activating the actuator device to drive said ink ejection device from a quiescent position to a pre-firing position; and deactivating said actuator device, thereby causing said recoil device to drive said ink ejection device to eject ink from said nozzle chamber via said ink ejection port.
 2. A method as claimed in claim 1 wherein said recoil device includes a resilient member and said movement of the actuator device results in resilient movement of said resilient member and said driving of the ink ejection device comprises the resilient member acting upon said ink ejection device.
 3. A method as claimed in claim 1 wherein said actuator device comprises an electromagnetic actuator.
 4. A method as claimed in claim 1 wherein said recoil device comprises a torsional spring.
 5. A method as claimed in claim 1 wherein said ink ejection device and said actuator device are interconnected in a cantilever arrangement wherein small movements of said actuator device result in larger movements of the said ink ejection device.
 6. A method as claimed in claim 5 wherein said recoil device is located substantially at a pivot point of said cantilever arrangement.
 7. A method as claimed in claim 1 wherein said actuator device includes a solenoid coil surrounded by a magnetic actuator having a first fixed magnetic pole and second moveable magnetic pole, such that, upon activation of said solenoid coil, said poles undergo movement relative to one another.
 8. A method as claimed in claim 7 wherein said moveable magnetic pole includes a plurality of slots for flowing ink through said pole upon movement of said moveable pole.
 9. A method as claimed in claim 1 wherein said ink ejection device comprises a piston or plunger having a surface substantially mating with at least one surface of the nozzle chamber. 